Can I approve an invoice that has been auto denied approval because it wasn't approved in 30 days?

Welcome to the Community, Marsha.

I'd be glad to help you resend your invoice that wasn't approved in QuickBooks Online (QBO).

To start, you have to create an Approval in the Custom workflow to resend the invoice that was undelivered or wasn't approved.

Here's how:

1. Go to the left navigation panel, and select Workflows.
2. Go to My Workflows, and click +Custom workflow.
3. Select Invoice and click Approval then select Next.
4. Name your workflow and click each box to customize your workflow for the invoice, you can also add a condition.
5. After that, click Save and enable.

After setting up the workflow, you can go to Sales and then Invoice to manually approve the Denied Approval or to resend it for approval.

For future reference, you can check this article to guide you receive and recording invoice payments in QBO: Record invoice payments in QuickBooks Online.

Please feel free to drop a comment below. If you have further concerns about the denied approval, workflow, or other QBO-related concerns. I will answer them in any possible way.